Reactive Decay Research Articles

Lunar simulant behaviour variability and implications on terrestrial based lunar testing

The detrimental effects and challenges of Lunar dust for Lunar exploitation were first identified during the Apollo missions. During the extra vehicle activities (EVAs) undertaken by astronauts, the dust clogged mechanisms, disrupted sensors, and caused several health issues for the astronauts. Despite numerous studies, there is no definite understanding as to why different Apollo missions experienced varying levels of dust disruptions. The variations in dust behaviour could be attributed to the amount of radiation the Lunar soil is exposed to, as well as mineralogy and particle sizes. To enhance our understanding of Lunar dust behaviour this study investigated Space Recourse Technologies, formally known as Exolith, simulant at different mineral compositions, and their surface detachment characteristics were measured. Experiments measuring the individual minerals and their mixed simulant-like counterparts were conducted using electrostatic fields. Inclusive to this, non-dried and dried samples were compared by measuring adhesion to target plates when subject to electrostatic forces. The results found that Highlands simulant exhibited a higher buildup on a target plate than its Mare counterpart by an average of 33% under the same conditions, likely due to particle size differences. In addition to these findings, evidence of particle reactivity decay was observed under repeated tests with up to 60% less Mare simulant and 36% Highlands deposition being measured compared to the first set of experiments. A possible explanation may be particle reactivity. Microscope images identified that particles are transported in groups as opposed to individual grains. These results will help researchers in tailoring dust mitigation solutions based on different regions on the Lunar surface and influence mission planning from the perspective of dust mitigation and contamination.

Possible alternative strategies to implement basophil activation testing in multicentric studies.

The Basophil Activation Test (BAT) enables flow cytometry characterization of basophil reactivity against specific allergenic molecules. The focus now revolves around democratizing this tool, but, as blood sample stability could be challenging, after having developed a simplified approach, herein, we aimed to characterize two strategies for implementing BAT in multicentric studies: store and ship blood before or after sample processing. Fresh heparin- and EDTA-anticoagulated whole blood samples followed both BAT workflows: "collect, store, process & analyze" or "collect, process, store & analyze". Storage temperatures of 18-25 °C or 2-8 °C and preservation times from 0 to 7 days were considered. Interleukin-3 was also evaluated. With the "collect, store, process & analyze" workflow, heparin-anticoagulated blood and 18-25 °C storage were better than other conditions. While remaining possible, basophil activation exhibited a possible reactivity decay after 24 h. Under the conditions tested, interleukin-3 had no role in enhancing basophil reactivity after storage. Conversely, the "collect, process, store & analyze" workflow demonstrated that either heparin- or EDTA-anticoagulated blood can be processed and kept up to 7 days at 18-25 °C or 2-8 °C before being analyzed. Various strategies can be implemented to integrate BAT in multicentric studies. The "collect, store, process & analyze" workflow remains a simplified logistical approach, but depending on time required to ship from the clinical centers to the reference laboratories, it might not be applicable, or should be used with caution. The "collect, process, store & analyze" workflow may constitute a workflow improvement to provide significant flexibility without impact on basophil reactivity.

Amine-bridged periodic mesoporous organosilica adsorbents for CO2 capture

Novel periodic mesoporous organosilica (PMOs) were synthesized using different commercial non-aminated and aminated bisilanes in order to incorporate aminated sites within the silica walls. Three different commercial bisilanes were employed: i)without amine groups, ii)with one amine group, and iii)with two amine groups. Moreover, materials were prepared with different molar ratios of non-aminated and aminated bisilanes. P123 was used as structure directing agent for the mesoporosity. The amino functional groups of the PMOs so prepared were incorporated within the silica walls of the obtained solid particles. Moreover, for comparative purposes, BEBA-0, that is a non-aminated PMO, was functionalized via grafting with N1-(3-trimethoxysilylpropyl)diethylenetriamine (DT) and impregnation with polyethyleneimine (PEI) to produce amino functionalized materials. All these materials were tested for CO2 capture through CO2 adsorption/desorption isotherms and TGA studies. It was observed that increasing the concentration of amine containing bisilane increased the CO2 capture capacity significantly from 21.4 mg/g to 47.3 mg/g. The PMO synthesized with the bisilane containing two amine groups had higher CO2 uptake than the one containing one amine group from 47.3 to 62.6 mg/g due to the presence of more functional groups in the final material (6.0 versus 9.4% wt N, respectively). The cyclic capacity of the adsorbents via a series of adsorption/desorption tests has also been determined, the results showing the low reactivity decay (less than 3%) of the novel PMOs and materials prepared by grafting during the first 10 cycles, when compared with the 13% of PEI-impregnated material.

Case studies on radioactivity and decay heat contribution from coating materials of irradiated accident tolerant fuel for a typical PHWR

Seven coating materials such as Al2O3, NbC, Si, SiC, TiN, Y2O3, and ZrC have been considered as a possible coating material towards development of accident tolerant fuel for a typical pressurized heavy water reactor. For an effective severe accident management strategy in addition to spent fuel handling, storage and transport, it is required to know the contribution to the radioactivity burden and decay heat load from the irradiated coating materials of accident tolerant fuel. Under irradiation of coating material in PHWR flux condition, the decay chain of each activated radionuclide has been simulated using ISOGEN code using one group homogenized point cross section. In this paper, radioactivity and decay heat contributions from different irradiated coating materials have been quantified and compared. The minimum contribution to radioactivity and decay heat is observed in SiC after irradiation of 445 days of normal operation. Out of all the coating materials considered in the study, most radioactivity and decay heat were added due to irradiation of coating materials Y2O3. From reactivity load, source term, and decay heat perspectives, silicon-based coating materials are found to be the most suitable.

Effect of CaO doping on the properties and crystallization behavior of Y2O3–Al2O3–SiO2 glass

Nowadays, Y2O3–Al2O3–SiO2 (YAS) glass joining is considered to be a promising scheme for nuclear-grade continuous silicon carbide (SiC) fiber reinforced SiC matrix composites (SiC/SiC). CaO has great potential for nuclear applications since it has low reactivity and low decay rate under nuclear irradiation. In this paper, the effect of CaO doping on the structure, thermophysical properties, and crystallization behavior of YAS glass was systematically studied. As the CaO doping content increased, the number of bridge oxygens and the viscosity at high temperatures reduced gradually. After heat treatment at 1400 °C, the main phases in YAS glass were β-Y2Si2O7, mullite, and SiO2 (coexistence of crystalline and glass phases), while that with 3.0% CaO doping turned into a single glassy phase under the same treatment conditions. Moreover, a structural model and the modification mechanism were proposed, which provided a theoretical basis for the subsequent component design and optimization.

CO2 capture performance of CaO-based sorbent modified with torrefaction condensate during calcium looping cycles

In this work, the organic acid-rich torrefaction condensate (TC) from biomass torrefaction process was attempted to replace commercial acetic acid (AC) for acidification treatment of CaO sorbent to improve its CO2 capture performance during calcium looping cycles. The results showed that TC-modified sorbents exhibited a much slower carbonation reactivity decay than the AC-modified one over the cycles. According to the results of characterizations (thermal decomposition, morphology, phase composition, and N2 adsorption), the enhanced cyclic stability was probably due to the presence of carbon deposition from the decomposition of heavy tar in TC, which might act as a spacer and protective overlay to slow down the sintering of CaO particles. In addition, more carbon deposition could be dispersed in-situ into the TC-modified sorbents by increasing torrefaction temperature and TC addition amount, resulting in more thorough carbon deposition overlay and better sintering resistance. However, excessive carbon deposition (>50 wt%) leaded to slightly lower carbonation conversions and rates in the first two or three cycles. But this deficiency would disappear in subsequent cycles, as some carbon deposition was consumed by the carbon dioxide released during calcination. And the carbonation conversion of TC-modified sorbent with a carbon deposition content of 69.1 wt% was still as high as 81.5% after 10 cycles.

Ghost Line Waves

Time-harmonic electromagnetic plane waves in anisotropic media can exhibit complex-valued wavevectors (with nonzero real and imaginary parts) even in the absence of material dissipation. These peculiar modes, usually referred to as “ghost waves”, hybridize the typical traits of conventional propagating and evanescent waves, displaying both phase accumulation and purely reactive exponential decay away from the direction of the power flow. Their existence has been predicted in several scenarios and has been recently observed experimentally in the form of surface phonon polaritons with complex-valued out-of-plane wavevectors propagating at the interface between air and a natural uniaxial crystal with slanted optical axis. Here, we demonstrate that ghost waves can arise also in lower-dimensional flat-optics scenarios, which are becoming increasingly relevant in the context of metasurfaces and in the field of polaritonics. Specifically, we show that planar junctions between isotropic and anisotropic metasurfaces can support “ghost line waves” that propagate unattenuated along the line interface, exhibiting phase oscillations combined with evanescent decay both in the plane of the metasurface (away from the interface) and out-of-plane in the surrounding medium. Our theoretical results, validated by finite-element numerical simulations, demonstrate a novel form of polaritonic waves with highly confined features, which may provide new opportunities for the control of light at the nanoscale and may find potential applications in a variety of scenarios, including integrated waveguides, nonlinear optics, optical sensing, and subdiffraction imaging.

Biomechanical induction of mild brain trauma in larval zebrafish: effects on visual startle reflex habituation.

A mild traumatic brain injury is a neurological disturbance of transient or/and chronic nature after a direct blow of the head/neck or exposure of the body to impulsive biomechanical forces, indirectly affecting the brain. The neuropathological events leading to the clinical signs, symptoms and functional disturbances are still elusive due to a lack of sensitive brain-screening tools. Animal models offer the potential to study neural pathomechanisms in close detail. We recently proposed a non-invasive protocol for inducing concussion-like symptoms in larval zebrafish via exposure to rapid linearly accelerating-decelerating body motion. By mean of auditory 'startle reflex habituation' assessments-an established neurophysiological health index-we probed acute and chronic effects that mirror human concussion patterns. This study aimed at expanding our previous work by assessing the ensuing effects with visual-as opposed to auditory-'startle reflex habituation' quantifications, by using the same methodology. We observed that immediately after impact exposure, the fish showed impaired sensory reactivity and smaller decay constant, possibly mirroring acute signs of confusion or loss of consciousness in humans. By 30-min post-injury, the fish display temporary signs of visual hypersensitivity, manifested as increased visuomotor reactivity and a relatively enlarged decay constant, putatively reflecting human post-concussive sign of visual hypersensitivity. In the following 5-24 h, the exposed fish progressively develop chronic signs of CNS dysfunction, in the form of low startle responsivity. However, the preserved decay constant suggests that neuroplastic changes may occur to restore CNS functioning after undergoing the 'concussive procedure'. The observed findings expand our previous work providing further behavioural evidence for the model. Limitations that still require addressment are discussed, advancing further behavioural and microscopic analyses that would be necessary for the validation of the model in its putative relatability with human concussion.

Rapid Assessment of Oxidative Damage Potential: A Comparative Study of Engineered Stone Dusts Using a Deoxyguanosine Assay.

The popularity of engineered stone (ES) has been associated with a global increase in occupational lung disease in workers exposed to respirable dust during the fabrication of benchtops and other ES products. In this study, the reactivity and subsequent oxidative reduction potential of freshly generated ES dusts were evaluated by (i) comparing different engineered and natural stones, (ii) comparing settled and respirable stone dust fractions and (iii) assessing the effect of ageing on the reactivity of freshly generated stone dust. An established cell-free deoxyguanosine hydroxylation assay was used to assess the potential for oxidative DNA damage. ES dust exhibited a higher relative reactivity than two of the three natural stones tested. Respirable dust fractions were found to be significantly more reactive than their corresponding settled fraction (ANOVA, p < 0.05) across all stone types and samples. However, settled dust still displayed high relative reactivity. The lower reactivity of the settled dust was not due to decay in reactivity of the respirable dust when it settled but rather a result of the admixture of larger nonrespirable particles. No significant change in respirable dust reactivity was observed for three ES samples over a 21-day time period, whereas a significant decrease in reactivity was observed in the natural stone studied. This study has practical implications for dust control and housekeeping in industry, risk assessment and hazard management.

Decay on Cyclic CO2 Capture Performance of Calcium-Based Sorbents Derived from Wasted Precursors in Multicycles

In order to obtain the cheap waste calcium-based sorbent, three wasted CaCO3 precursors, namely carbide slag, chicken eggshells, and analytical reagent-grade calcium carbonate, were selected and prepared at 700 °C to form calcium-based sorbents for CO2 capture. TGA was used to test the CO2 uptake performance of each calcium-based sorbent in 20 cycles. To identify the decay mechanism of CO2 uptake with an increasing number of cycles, all calcium-based sorbents were characterized by using XRF, XRD, and N2 adsorption. The specific surface area of calcium-based sorbents was used to redefine the formula of cyclic carbonation reactivity decay. The carbonation conversion rate of three calcium-based sorbents exhibited a decreasing trend as the cycle number increased. Chicken eggshells exhibited the most significant decrease rate (over 50% compared with Cycle 1), while carbide slag and analytical reagent-grade calcium carbonate showed a flat linear decline trend. The specific surface area of the samples was used to calculate carbonation conversion for an infinite number of cycles. The carbonation conversion rates of three calcium-based sorbents were estimated to decrease to 0.2898, 0.1455, and 0.3438 mol/mol, respectively, after 100 cycles.

Steam-enhanced calcium-looping performance of limestone for thermochemical energy storage: The role of particle size

Steam injection has been proposed to attenuate the decay of CaO reactivity during calcium looping (CaL) under operating conditions compatible with carbon capture and storage. However, it is yet unknown whether the perceived advantages granted by steam hold under the distinct operating conditions required for the integration of the CaL process as a thermochemical energy storage system in Concentrating Solar Power Plants (CaL-CSP). Here, we study the influence of steam in conditions compatible with a CaL-CSP scheme and assess its impact when injected only during one stage; either calcination or carbonation, and also when it is present throughout the entire loop. The results presented here demonstrate that steam boosts the CaO multicycle performance in a CO2 closed loop to attain residual conversion values similar to those achieved at moderate temperatures under inert gas. Moreover, it is found that the enhancement in multicycle activity is more pronounced for larger particles.

Quantitative and Sensitive Mid-Infrared Frequency Modulation Detection of HCN behind Shock Waves

Despite its key role for the study and modeling of nitrogen chemistry and NOx formation in combustion processes, HCN has only rarely been detected under high-temperature conditions. Here, we demonstrate quantitative detection of HCN behind incident and reflected shock waves using a novel sensitive single-tone mid-infrared frequency modulation (mid-IR-FM) detection scheme. The temperature-dependent pressure broadening of the P(26) line in the fundamental CH stretch vibration band was investigated in the temperature range 670K≤T≤1460K, yielding a pressure broadening coefficient for argon of 2γAr296K=(0.093±0.007)cm−1atm−1 and a temperature exponent of nAr=0.67±0.07. The sensitivity of the detection scheme was characterized by means of an Allan analysis, showing that HCN detection on the ppm mixing ratio level is possible at typical shock wave conditions. In order to demonstrate the capability of mid-IR-FM spectroscopy for future high-temperature reaction kinetic studies, we also report the first successful measurement of a reactive HCN decay profile induced by its reaction with oxygen atoms.

Effect of calcination condition on the performance of iron ore in chemical-looping combustion

The calcination of oxygen carrier is the essential step prior to its application in chemical looping combustion, which is significantly influenced by calcination conditions. In this study, a natural iron ore was treated under the combined effect of three key calcination parameters (heating rate, temperature, and duration time). The reactivity performance of calcined iron ores was evaluated with CO as fuel, and the iron ore with the best performance and the parameter with the greatest impact were screened. The results showed that the iron ores treated under different calcination conditions showed evident difference in their reactivity, in which calcination temperature showed the biggest impact on the physicochemical properties of fresh iron ore. The best calcined iron ore was obtained under the heating rate of 15 °C/min, the temperature of 1050 °C, and the duration time of 60 min within the selection limits of three calcination parameters, and its cyclic test showed that the maintained good physical structure of best calcined iron ore guaranteed it against the reactivity decay, a stable recyclability performance was achieved during the consecutive redox cycles. The findings in this study could provide a reference for the further optimization of calcination parameters suitable for commercial oxygen carriers.

The two-component model coincidence: Evaluating the validity of marine dissolved organic radiocarbon as a stable-conservative tracer at Station M

This study examines the applicability of the two-component mixing model in one dimension (depth) to published depth profiles of DOC concentrations and Δ14C values from hydrographic Station M (34°50′N, 123°00′W). We have rederived the two-component model assuming DOC exhibits stable conservative tracer properties and compared it to a model that includes reactivity and radioactive decay. We used 14C∗, the fractionation- and decay-corrected concentration of 14C atoms in DOC or DIC, as a new tool for evaluating the two-component model and carbon biogeochemistry at Station M. All relationships between DOC and other tracers predicted under this framework exhibited sharp discontinuities (“cusps”) at ~85–~250 m depth. Below the cusps, the best fit relationships to the depth profiles yielded negligible DOC reaction rates consistent with conservative mixing. These observations separate the water column into two distinct biogeochemical regimes, with the apparent dominance of production and consumption of more labile DOC constituents in the epipelagic, and physical mixing at depths below the cusp. Our results indicate DO14C∗ vs. DI14C∗ correlations are more precise tools than comparisons with Δ14C or salinity, for identifying regions with unique DOC biogeochemistry that are currently obscured by measurement uncertainties and natural variability in traditional two-component model analyses, such as Keeling Plots. Higher resolution observations are required to precisely locate the cusps and understand their relationship to the separation of more labile DOC in the surface from more conservative DOC at depth. These results do not refute the two-component model, but rather support it as a simplified approximation to the complex biogeochemical processes that vary throughout the water column. In this way, DOC concentrations and Δ14C values can be approximated as a semi-conservative tracer for select applications.

Modeling the deactivation of CaO-based sorbents during multiple Ca-looping cycles for CO2 post-combustion capture

A novel model is presented for the estimation of natural CaO-based sorbents carbonation reactivity decay during Calcium Looping carbonation-calcination cycles. The model consists of a cyclic framework of two sub-models, the Overlapping Grain Model and the novel proposed modified Rate Theory for the Pore Size Distribution model. The model was implemented in gPROMS ModelBuilder® and parameter estimation was used for model validation using experimental data from three CaO-based sorbent precursors. The carbonation profile for the three sorbents was simulated with average deviations under 5%. The calcination sub-model predicted the evolution of total porous volume and total surface area for the calcination and sintering of dolomite, with an error of 3%. The cyclic framework successfully predicted the carbonation behavior of dolomite for 20 carbonation-calcination cycles. The model can be used for other CaO-based sorbents and the flexible modular structure allows the integration of other modules or approaches.

High-Efficiency CaO-Based Sorbent Modified by Aluminate Cement and Organic Fiber Through Wet Mixing Method

CaO-based sorbents are usually used for high-temperature postcombustion CO2 capture through cyclic carbonation–calcination reactions. However, the rapid decay of sorbent reactivity limits their application. In this study, three types of CO2 sorbent precursors, namely Ca(CH3COO)2, Ca(OH)2, and CaCO3, are used to produce initial CaO-based sorbents. Then, the initial sorbents are mixed with aluminate cement and organic fibers at an appropriate ratio to synthesize high-efficiency sorbents. Our results show that the cyclic performance of the sorbent that decomposed from Ca(CH3COO)2 is better than that decomposed from Ca(OH)2 and CaCO3. It is mainly because the sorbent pore structure becomes much developed after Ca(CH3COO)2 decomposition. Furthermore, when mixed with aluminate cement, the CaO-based sorbent achieves a good performance for CO2 capture because of the formation of the sorbent skeleton Ca12Al14O33. For example, when the mass ratio of Ca(OH)2 to aluminate cement is set as 1:1, CaO conversion achieves...

Effect of Seawater, Aluminate Cement, and Alumina-Rich Spinel on Pelletized CaO-Based Sorbents for Calcium Looping

Calcium looping (CaL) is considered as an emerging technology to reduce CO2 emissions in power generation systems and carbon-intensive industries. The main disadvantage of this technology is reactivity decay over carbonation/calcination cycles due to sintering. The main objective of this study was to evaluate the performance of novel sorbents for CaL. Three types of pelletized CaO-based sorbents for CO2 capture were developed by adding aluminate cement, aluminate cement with seawater, or alumina-rich spinel to calcined limestone. Different concentrations of seawater in deionized water solutions were tested: 1, 10, 25, and 50 vol %. All samples were tested in a thermogravimetric analyzer (TGA) under two different calcination conditions: mild (N2 atmosphere and 850 °C during calcination) and realistic (CO2 atmosphere and 950 °C during calcination). The samples were characterized using SEM and EDX. Aluminate cement CaO-based sorbents exhibited better performance in the TGA tests (25% conversion after 20 cycl...

Comparison of pyrite cinder with synthetic and natural iron‐based oxygen carriers in coal‐fueled chemical‐looping combustion

AbstractPyrite cinder, a Fe2O3‐containing industrial waste derived from the sulfuric acid manufacturing industry, was compared with the synthetic and natural iron‐based oxygen carriers, to explore its potential superiority in coal‐fueled chemical‐looping combustion. The oxygen carriers were evaluated through a lab‐scale fluidized‐bed reactor regarding their reactivity, recyclability, and attrition performance. The results showed that pyrite cinder prevailed over synthetic and natural iron‐based oxygen carriers in terms of the reactivity. Similar CO2 yields were obtained by both pyrite cinder and synthetic Fe‐Al(10nm) oxygen carrier, but the char conversion rate for pyrite cinder was obviously higher than that of synthetic and natural iron‐based oxygen carriers. As for the cyclic reaction behavior, both pyrite cinder and natural MAC iron ore performed well regarding the stable yield of CO2, whereas synthetic Fe‐Al(10nm) oxygen carrier showed a poor resistance to the decay of reactivity and occurrence of severe sintering. The attrition performance of three oxygen carriers under different operation parameters showed that the particle collision and the collisions between oxygen carrier particle and reactor wall were the major triggers to the attrition. The cyclic attrition tests showed that the abrasion‐resistant capability for the pyrite cinder pelletized by the double‐roller squeezing granulation method was lower than that of synthetic and natural iron‐based oxygen carriers. It can be concluded that the pyrite cinder would be an outstanding candidate as the iron‐based oxygen carrier, but its mechanical strength should be enhanced before produced in large scale. © 2017 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Effect of Iron Coating on Thermal Properties of Aluminum‐Lithium Alloy Powder

AbstractAluminum‐lithium alloys are widely studied to improve performance in energetic materials. However, their high reactivity causes severe surface oxidation over micro‐Al particles in storage, resulting in significant deterioration in the overall performance. This study deals with the effect of iron coating on thermal properties and aging stability of aluminum‐lithium alloy powder. Gas atomized Al‐3Li (3 wt. %) alloy powder was prepared and then successfully coated with nano‐sized iron film by modified chemical liquid deposition method. The morphology, thermal properties and combustion enthalpies were characterized by SEM/EDX, TG/DTA and oxygen bomb calorimeter. The results showed that Fe/Al‐3Li composite powder presented obvious core‐shell structure and the outer iron film was very uniform and compact. Significantly enhanced thermal reactivities of Al‐3Li alloy powder and Fe/Al‐3Li composite powder were achieved compared with pure Al. In addition, aging studies indicated that, after coating, the reactivity decay rates of alloy powder decreased significantly, and the mass combustion enthalpies remained basically stable, which demonstrated that iron coating indeed prevented pre‐oxidation of the alloy powder and improved its aging stability.

Improving Efficiency and Durability of Dual-Photoelectrode Water-Splitting Devices

Utilization of solar light energy for water splitting and production of hydrogen, on the future industrial basis, will be performed in a mass-scale chemical plant involving lots of photocatalytic light-harvesting panels. Within those panels, not only the photocatalysts but also many other functional mechanisms will be included in order to feed and circulate the reactant water, to eject and lead the product gases safely, and to maintain the conditions of the catalysts and water for stable operation. All those functionalities consume energy, whereas the energy production is made only by the photocatalysts. As an energy-producing plant, the production and self-consumption of energy should be balanced so as to gain a profitable amount of energy. We are now focusing on the operational technologies for our laboratory-class solar light-driven water splitting devices towards higher energy conversion efficiency and durability, taking this balance into our consideration. Choice of the light-absorbing materials as well as co-catalysts for H2/O2evolution is the most important issue to realize satisfactory efficiency. Indeed most of our efforts are dedicated for research of materials suitable for light harvesting. To foster material research in this sense, we adhere to photocatalytic or photoelectrochemical devices without photovoltaics or external power supply as the main power source. We are intensively investigating several semiconductive candidate materials, such as oxides [1,2], nitrides, oxynitrides [3-5] and other chalcogenides [6-9] of transition metals for both photocathodes and photoanodes. The key issues in selecting the target materials are the light absorption spectrum in the solar region, the optimized photoelectrochemical current density, the onset potential of photoelectrochemical curves, and the durability after appropriate co-catalyst and protective coating. We chose pairs of photocathodes and photoanodes out of these materials of our own development, and assemble prototype water-splitting photo-cells. A finite non-zero photo-electrolysis current is obtained when the cyclic photo-voltammetric curves of the cathode and the anode cross over each other under light irradiation in the same electrolytic solution. This is a prerequisite of our water splitting device and is still a limiting issue for the choice of electrode materials for a highly efficient water-splitting device. The content of operational solution and, in particular, the pH of the solution are also important in the dual electrode operation. Naturally the optimal pH for the photocathode alone is different from that for photoanode alone, and we must adjust the solution pH at the median of those two, as long as the electrodes are not deactivated. The reactivity of co-catalysts are often dependent on the solutes. Phosphate, sulfate and borate buffers are the typical choices. The durability of water-splitting devices is related to the maintenance of catalyst surface activity and stabilization of chemical and physical status of the aqueous solution near the catalyst surface. To prevent or delay the chemical degradations of photocatalyst surfaces, we are developing protective layers that are electron/hole conductive and chemically inert. Physically, the sizes and arrangement of photocatalytic plates can facilitate the microscopic circulation of aqueous species near them. The rapidest decay of reactivity is usually due to building-up inhomogeneity of solute distribution between the two photoelectrodes during operation, often called “pH gradient”. This inhomogeneity will be cancelled by stirring, pumping or circulating the solution, or by applying the inverse voltage between the electrodes. We are trying to work out how efficiently these mechanical/fluidic and electrochemical issues are solved in order to conserve the extra energy for those costs. In this talk some specific examples of materials and technologies from our group will be presented, and some benchmark devices with notable efficiency and durability for solar powered water splitting will be described.